Alien world is blacker than coal

Aug 11, 2011

The distant exoplanet TrES-2b, shown here in an artist's conception, is darker than the blackest coal. This Jupiter-sized world reflects less than one percent of the light that falls on it, making it blacker than any planet or moon in our solar system. Astronomers aren't sure what vapors in the planet's superheated atmosphere cloak it so effectively. Credit: David A. Aguilar (CfA)

(PhysOrg.com) -- Astronomers have discovered the darkest known exoplanet - a distant, Jupiter-sized gas giant known as TrES-2b. Their measurements show that TrES-2b reflects less than one percent of the sunlight falling on it, making it blacker than coal or any planet or moon in our solar system.

"TrES-2b is considerably less reflective than black acrylic paint, so it's truly an alien world," said astronomer David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author on the paper reporting the research.

In our solar system, Jupiter is swathed in bright clouds of ammonia that reflect more than a third of the sunlight reaching it. In contrast, TrES-2b (which was discovered in 2006 by the Trans-Atlantic Exoplanet Survey, or TrES) lacks reflective clouds due to its high temperature.

TrES-2b orbits its star at a distance of only three million miles. The star's intense light heats TrES-2b to a temperature of more than 1,800° Fahrenheit - much too hot for ammonia clouds. Instead, its exotic atmosphere contains light-absorbing chemicals like vaporized sodium and potassium, or gaseous titanium oxide. Yet none of these chemicals fully explain the extreme blackness of TrES-2b.

"It's not clear what is responsible for making this planet so extraordinarily dark," stated co-author David Spiegel of Princeton University. "However, it's not completely pitch black. It's so hot that it emits a faint red glow, much like a burning ember or the coils on an electric stove."

Kipping and Spiegel determined the reflectivity of TrES-2b using data from NASA's Kepler spacecraft. Kepler is designed to measure the brightnesses of distant stars with extreme precision.

The team monitored the brightness of the TrES-2 system as the planet orbited its star. They detected a subtle dimming and brightening due to the planet's changing phase.

TrES-2b is believed to be tidally locked like our moon, so one side of the planet always faces the star. And like our moon, the planet shows changing phases as it orbits its star. This causes the total brightness of the star plus planet to vary slightly.

"By combining the impressive precision from Kepler with observations of over 50 orbits, we detected the smallest-ever change in brightness from an exoplanet: just 6 parts per million," said Kipping. "In other words, Kepler was able to directly detect visible light coming from the planet itself."

The extremely small fluctuations proved that TrES-2b is incredibly dark. A more reflective world would have shown larger brightness variations as its phase changed.

Kepler has located more than 1,200 planetary candidates in its field of view. Additional analysis will reveal whether any other unusually dark planets lurk in that data.

TrES-2b orbits the star GSC 03549-02811, which is located about 750 light-years away in the direction of the constellation Draco. (One light-year is about 6 trillion miles.)

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@Titto, not only were the first extrasolar planets discovered in 1992, Kepler wasn't launched until 2009, and currently monitors more than 100,000 stars simultaneously. So perhaps the astrophysical world can be forgiven if they didn't notify you of this important discovery sooner.

What you're smelling is your own stupidity. Perhaps you should wander back to the FoxNews web site to share your conspiracy theories.

I wish they would explain why they chose this explanation over other possible explanations. To start off with, while we watch the planet, it is tidally locked, and we would only be able to detect an average of 25-30% of the reflected light (while it is in view) to begin with. Second, this planet is so close to the star, and could very well be within the corona or obscured by it much of the time - therefore, a lot of reflected light from the planet would be absorbed, obscured, and washed out by the coronal emissions.

I'm not saying that they're wrong, but when making such a bold claim, perhaps they should explain how they came to their conclusion over other more immediate explanations.

Katanuuv, the planet wasn't discovered by Kepler. It was discovered by TrES in 2006. It says that in the ARTICLE. If you don't know how to read perhaps you should wander back to the MSNBC website where your blatherings will be welcome.

"Morpheus: We don't know who struck first, us or them. But we do know it was us that scorched the sky. At the time, they were dependent on solar power. It was believed they would be unable to survive without an energy source as abundant as the sun." Let's call it the Matrix planet. :)

Well......not if you check the washington post of 1983 and the dates when Sedna was discovered?? That is way back my friend!!

Where the hell are you getting your BS: 1) Sedna is a Solar dwarf planet. 2) It was discovered in 2003. And that's not so long ago, my friend. Anyone can look this up in 10s flat, so what's your problem? Are you in any way related to Rip Van Winkle? ARE YOU Rip Van Winkle???